test: clean up test-timers-immediate
Checklist
-
make -j8 test
(UNIX), orvcbuild test nosign
(Windows) passes -
commit message follows commit guidelines
Affected core subsystem(s)
test tools
Description of change
Clean up test-timers-immediate. Use of let
also requires a tweak to
ESLint rules (but it's one that we should do as timers is pretty much
the reason it exists).